Ecologically and economically it is important to prevent loss of mercury from industrial processes. Operation of mercury cathode alkali-chlorine brine electrolysis cells is a significant source of inductrial mercury consumption. Mercury solubilized in the depleted cell brine is normally returned to the electrolysis cell. However, some mercury escapes from the electrolysis process cycle when insoluble waste products designated "sludge" are purged from the electrolysis operation.
Sludge may originate in the cell brine or the cell apparatus. It is particularly troublesome to remove mercury contained in sludges associated with perification or resaturation of the brine because the mercury is often contained in insoluble form at levels below 100 parts per million.
U.S. Pat. No. 3,600,285 describes a carbon sorption process for removing mercury solubilized in electrolysis cell brine. The patent describes reuse of recovered mercury in the electrolysis cell but cautions that recovered mercury be reintroduced to the cell after brine alkalization because mercury may be lost in the alkalizing mud.
U.S. Pat. No. 1,637,481 teached the recovery of mercury from cinnabar ore by slightly acidifying a paste of the ore to destroy basicity prior to reaction with hypochlorite and a metal.
Mercury removal from ores by leaching with aqueous hypochlorite solvent is described in numerous references. For example, G. A. Parks and N. A. Fittinghoff's "Mercury Extraction Now Possible Via Hypochlorite Leaching", E/MJ, June 1970, Pages 107-109, and U.S. Pat. No. 3,627,482 to R. S. Olson et al. describe the desirability of avoiding highly acidic leaching solutions because of corrosion and the relative instability of the hypochlorite ion.
The isolation of solubilized mercury may be accomplished by a variety of techniques such as precipitation, adsorption, or electrolysis as described in U.S. Pat. No. 3,476,552 issued Nov. 4, 1969.